Method for recovery of rosin soap material from spent wood liquors



Patented Oct. 14, 1930 UNITED STATESPATENT OFFICE VIGGO DREWSEN, OFLARCHMON'I, NEW YORK, ASSIGNOR TO WEST VIRGINIA PULP AND PAPER COMPANY,OF NEW YORK, N. Y., A CORPORATION OF DELAWARE METHOD FOR RECOVERY OFROSIN SOAP MATERIAL FROM SPENT WOOD LIQUORS Ho Drawing.

This invention relates to the recovery of a rosin soap material fromspent liquors resulting from the cooking of coniferous woods for themanufacture of paper pulp or other purposes.

When coniferous woods are cooked with alkaline liquors or with sodiummonosulphite liquors. rosin and fatty acids in the wood are saponifiedand become incorporated in the.

be salted out of the liquor and if suitably concentrated liquor isallowed to stand and cool sufliciently, the soaps will collect as a scumat the top. In the practice, however, cooling and settling of theconcentrated spent liquor sufficiently to recover good yields of thesoapy content is uneconomical since it wastefully dissipates heat thatcan be used advantageously in further treating the liquor for recoveryof chemicals therein or in the preparation.t-hereof for burning.Moreover, the removal of the soap from the settling apparatus involveslaborious time-consuming work. The formation of soap scums in the laterstages of the evaporators in which spent liquors are commonlyconcentrated is generally regarded in the industry as a cost ly nuisancenecessitating frequent cleaning of the evaporators rather than as thesource of a valuable by-product. Ordinarily the evaporators andparticularly the third and fourth effects have to be cleaned weekly toremove soap scums. Moreover, after each cleaning the efliciency of theevaporators again falls oif continuously due to the accumulation ofthicker and thicker soap scums.

Various methods for recovering soapy materials from such spent liquorshave heretofore been suggested but none of them have provensatisfactory.

Application filed January 11, 1928. Serial No. 246,095.

According to the present invention, the

spent liquor may be passed continuously through a centrifugal separatorwhereby the soapy materials are continuously removed and flow tosuitable soap vats and the soapfree liquor returned to the concentratingsys- I tem. The separating machine may advantageously be of the typecommonly used for separating cream from milk or of the type colmmonlyused for separating water from 01 proper concentration and temperatureat the time when it is run into the separating machine. Concentration ofthe spent liquor automatically effects a gradual salting out of thesoapy constituents therein. The salting out action is also increasedasthe temperature of the liquor falls. Temperatures below 60 C. areusually needed for good yields. The temperature should be high enough,however, so that the soap can be freelyflowed through the separatingmachine and it is desirable to avoid temperatures so low as to depositsoap in the evaporators prior to the sending of the liquor to theseparating machine. Usually the temperature should be It is important tohave the liquor at a above 25 C. The liquor at the time of treat-'materials saltedout of the spent liquor are largely dispersedthroughout the liquor in tiny liquid globules like cream in milk. Theconcentration must be carried to a stage at which the gravity of theliquid is materially different from the gravity of the soapy materials.For exam le, when the specific gravity of the soap is :1 out 1.05, thespent liquor should be evaporated to a specific gravity between about1.1 and 1.15; on the other hand, with a soap having a gravity of 1.13 agood separation has been accomplished with a'liquor of 1.10, the flow ofseparated soap and liquor being reversed. The optimum specific gravityand temperature for the contained and the gravity and solubility of thesoap. Optimum conditions for a particular plant and liquor may readilybe deterform at about 45 C.

mined in accordance with the foregoing principles as indicated by thefollowing example.

A certain spent liquor was subjected to evaporation in a series ofmultiple effect evaporators in accordance with standard practice. Theliquor, as delivered to the evaporator and as it existed after passagethrough one eifect of the evaporator, was found to be too dilute toyield substantial separation if passed through a centrifugal machine. ofthe evaporator, the liquor was approximately halved in volume andconsequently doubled in concentration so that it then approximated aspecific gravity of 1.10. The salts dissolved in the spent liquor had bythis time become sufficiently concentrated to effect at the temperatureprevailing in the evaporator an automatic salting out of a substantialportion of the dissolved soap in the form of tiny globules almostcolloidally dispersed throughout the spent liquor. The existence of theseparated globules was, of course, invisible to the eye in the blackliquor just as the cream is invisible in fresh milk. It was foundconvenient to test the extent of the salting out of the soap in theliquor at each stage by whirling a small sample in in ordinary Babcockmilk testing centriuge.

The indications afforded by the Babcock machine in this instance wereconfirmed by passing the liquor from the second effect through a DeLaval or a Sharpless separator at different temperatures. Practically noseparation of soap occurred at temperatures of C. or over. About 3 lbs.per 100 gals. was recovered at 60 (3., about 5.8 lbs. per 100 gals. at50 C., about 6.5 lbs. per 100-gals. at 45 (1., and about 7.4 lbs. per100 gals. at 42 C. This was about as cool as it seemed de sirable tocool the liquor although slightly greater recoveries were obtained bycontinuing the cooling down to 25 C.

It was found that liquor taken after passing through three effects ofthe evaporator had become too concentrated for treatment 1n thecentrifugal machine asit yielded only one and a half pounds'per 100gals, the reason being that most of the soap had already separated outand been deposited in the third efiect of the evaporator. For thisparticular plant and type of liquor, therefore, it seemed deslrable totake the liquor from the second stage of the evaporator. The tem-.perature of 11 nor from the second evaporator averaged a out 45 C. butwas subject to fluctuations. It was found desirable to provide means forkeeping its temperature uni- It was found desirable to warm thedischarge passage for the soap from the separating machine so as toprevent congealing of the soap on the walls and gradual contraction ofthe passage.

After passing through two effects The soap material, which flowed fromthe separator, was practically free from residual liquor. It yielded aclear amber colored solution with water. A typical sample had a specificgravity of about 1.049 and contained about 36% of rosin acids and 23% offatty acids and about 34% moisture. The total alkali computed as Na Owas about 4.37. This soapy mixture makes an excellent size. It is alsouseful as a soap stock.

It will be obvious from the foregoing that the method and process may bemodified in many details without departing from the spirit and scope ofmy invention.

What I claim is:

1. A method of recovering soaps dissolved in spent wood treating liquorwhich comprises concentrating the liquor to a specific gravity ofapproximately 1.1 to 1.15, and at which the gravity of the liquordiffers from the gravity of the soap, and subjecting such liquor at atemperature between about 25 to 60 degrees Centigrade to centrifugalseparation.

2. A process for the recovery of soap from spent wood treating liquorswhich comprises evaporating the spent liquors to a concentration whereatthe gravity of the liquor differs from the gravity of the soap therein,subjecting such concentrated liquor at a temperature at which the soapis largely dispersed through the liquor in minute globules tocentrifugal separation and collecting said soap.

3. A process for the recovery of soap from spent wood treating liquors,which comprises concentrating the liquor until the specific gravity ofthe liquor differs from the specific gravity of the soapy constituentstherein and soapy constituents have been salted out, subjecting suchconcentrated liquor to centrifugal separation and collecting said soap.

4. A process for the recovery of soaps from spent wood treating liquors,which comprises concentrating the liquor until the specific gravity ofthe liquor differs from the specific gravity of the soapy constituentstherein and soapy constituents have been salted out, subjecting suchconcentrated liquor to centrifugal separation at a temperature between25 C. and 60 0., and collecting said soap.

5. A continuous process for the treatment of spent wood treating liquorscontaining soap WlllCll comprises evaporating the spent liquors to aconcentration whereat the gravity of the liquor differs from the gravityof the soap therein, subjecting such concentrated liquor to centrifugalseparation at a temperature at which the soap is largely dispersedthrough the liquor in minute globules, col- 1 lecting the soap, andreturning the separated liquor for further concentration.

6. A continuousprocess for the treatment of spent wood treating liquorscontaining soap which comprises concentrating the liqnor until thespecific gravity thereof differs from the specific gravity of the soapyconstituents therein and soapy constituents have been salted out,subjecting such concentrated liquor to centrifugal separation at atemperature between 25 C. and C., collecting the soap, and returning theseparated liquor for further concentrat on.

} In testimony whereof, I have signed my name to this specification this9th day of January, 1928.

VIGGO DREWSEN.

